Both the engineers were employed by the Nguyen Phuc Company, a contractor working on the Nuoc Trong Bridge. The men's duty was to maintain traffic safety around the construction site.

However, following a pair of traffic accidents that killed three people in April and May, police found that the site was dangerously underlit at night and that none of the warning signs could be seen after dark.

According to police, the first accident occurred on April 8 when Tran Minh Duong, 24, crashed into a divider. The young man died at the scene.

On May 11, Dang Duc Tuan, 20, and Bach Van Ton, 20, died after crashing a motorbike into the same divider.

Police are investigating the case further.

The Nuoc Trong Bridge is part of a project to extend National Road 51, which was launched in August 2009 with a total investment of VND3.3 trillion (US$156.6 million).